Post-Only is a tool for smart trading: a complete guide

Post-Only is a special option for limit orders that prevents them from being executed automatically at an unfavorable moment. The main idea is simple: when you place a limit order with this option, the system guarantees that the order will remain in the order book or be canceled, but never turn into a market order. This means you always pay the maker fee, not the taker fee.

The Post-Only feature is available in spot trading (for users of the Unified Trading Account) as well as in perpetual and futures contracts, for both standard accounts and UTA.

Cost Savings: The Main Advantage of Post-Only

The most important benefit of Post-Only is the ability to reduce trading costs. When you trade large volumes, even a small difference in fee size matters. The maker fee (for liquidity providers) is always lower than the taker fee (for liquidity takers). Post-Only guarantees that you will pay the lower rate.

How the system protects your order from unexpected execution

When the market is highly volatile, prices move quickly. The system monitors the moment you place your order and analyzes the current order book state. If, at the time of placing a limit order, there is an opportunity for immediate execution (i.e., the price matches or is better than your order), the system automatically cancels the order instead of filling it. This prevents accidental switching to market execution and the higher associated fees.

Practical Example: What Happens in a Volatile Market

Imagine a scenario with the BTCUSD pair during active price fluctuations:

A trader places a long buy order for 100,000 contracts at $9,000. At the moment of order creation, the best bid in the order book is $9,001. But by the time the order reaches the system, the best available price has already dropped to $8,995.

Scenario A: Without Post-Only Protection

Since the order book has shifted favorably (8,995 < 9,000), the system automatically converts the limit order into a market order and fills it at the best available price. The trader gets filled but unexpectedly pays the taker fee instead of the cheaper maker fee. Remember, the actual execution also depends on the chosen Time-In-Force (TIF) strategy — for example, GTC (Good-Till-Canceled), IOC (Immediate-or-Cancel), or FOK (Fill-or-Kill).

Scenario B: With Active Post-Only Protection

When the order book shifts to a better price (8,995 < 9,000), creating a risk of immediate execution, the system automatically cancels the order. The order is not converted into a market order. The trader remains safe and avoids paying unexpectedly high taker fees.

Maker vs. Taker: Why This Difference Matters

A maker is a market participant who adds liquidity by placing an order in the order book. A taker is someone who takes existing orders from the book. Exchanges incentivize makers with lower fees and penalize takers with higher fees. Post-Only ensures you remain a maker and receive a more favorable rate.

Where Post-Only works

• Spot trading: for users of the Unified Trading Account (UTA)
• Perpetual contracts: for all user types
• Futures contracts: for both standard accounts and UTA

Summary: Post-Only is not just an option, it’s an investment in efficiency

Post-Only is a powerful tool for traders who want full control over their fee expenses. With automatic protection against unexpected execution, you always know what fee you’re paying, especially when trading large volumes during volatility. This makes your trading more predictable and more cost-effective.